(a) Field of the Invention
The present invention generally relates to a semiconductor device and a method for forming a metal line in the semiconductor device. More particularly, the present invention relates to a semiconductor device and a method for forming a metal line in the semiconductor device having an advantage of reduced contact resistance.
(b) Description of the Related Art
As semiconductor devices become more integrated, metal lines are usually fabricated in a multi-layer structure.
FIG. 2A to FIG. 2E are cross-sectional views showing sequential stages of a conventional method for forming a metal line in a semiconductor device.
Referring to FIG. 2A, metal layer 204 may be formed on semiconductor substrate 202 by depositing a metal material thereon by a physical vapor deposition (PVD) method, an ion beam method, an electron beam method, or a radio-frequency (RF) sputtering method, for example. Then, photoresist pattern 206 for etching the metal layer 204 can be formed on metal layer 204.
Subsequently, as shown in FIG. 2B, metal layer 204 can be dry etched according to photoresist pattern 206. Thus, lower metal line 204a may be formed on semiconductor substrate 202. Then, a cleaning process is performed and photoresist pattern 206 may be removed.
As shown in FIG. 2C, insulator layer 208 can be formed on semiconductor substrate 202 and lower metal line 204a by depositing an insulating material, such as a high density plasma (HDP) oxide layer. Then, a surface of insulator layer 208 may be planarized by a chemical mechanical polishing (CMP) process, for example.
In addition, as shown in FIG. 2D, photoresist pattern 210 for forming a contact hole can be formed on insulator layer 208.
Now, insulator layer 208 may be etched using photoresist pattern 210 and, accordingly, contact hole 212 for a contact to lower metal line 204a may be formed, as shown in FIG. 2E. Then, photoresist pattern 210 can be removed.
Here, a metal material can then be filled into contact hole 212 so as to form a contact electrode (not shown), and then an upper metal line (not shown) can be formed by depositing a metal material by various methods, such as an ion beam method, an electron beam method, or an RF sputtering method.
A continuing trend in semiconductor devices is that an available area per device has been reduced due to higher integration of the semiconductor devices. Thus, a size of a contact hole connecting two metal lines or a semiconductor substrate and a metal line has been also reduced. Furthermore, widths of metal lines have also been reduced. Therefore, in this case, contact resistance may be excessively increased when a semiconductor device is made according to such a conventional method. That is, an effective contact area may be problematic for a semiconductor device that has been highly integrated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form prior art or other information that may be already known in this or any other country to a person of ordinary skill in the art.